This invention relates to the field of communications. More particularly, a system and methods are provided for enabling telephone connections to be established between analog and digital telephone service subscribers without the use of a traditional analog/digital gateway.
Although the form of telephone communications is rapidly changing from analog to digital, the huge installed based of analog, or POTS (Plain Old Telephone System/Service), connections requires changes or evolutions in telephone communications to be compatible with POTS. The number of POTS subscribers far exceeds the number of digital subscribers, thus making it necessary to interface or transfer calls between the digital and analog systems.
Telephone communications are more and more often carried in digital form between central offices (CO), using both private and public (e.g., the Internet) digital networks, particularly for long distance calls. Most telephone calls still involve a conventional, analog, device at one end or the other; therefore at each end of the call, a telephone company""s CO must be involvedxe2x80x94either to receive the call from the local loop that serves the calling party or, at the other end, to place it on the local loop serving the called party.
Presently, in order to complete a call to an analog (POTS) subscriber, where the call was originated from a digital subscriber and/or carried to the called party""s CO digitally, a central gateway must handle the call and translate it from digital to analog form. For example, voice over Internet services are quite popular and allow one POTS subscriber to talk to another without long-distance tolls. In particular, the voice communications are routed digitally (e.g., over the Internet), with a gateway at each end to convert the voice between analog and digital forms.
Gateways are typically located at central offices and may be responsible for the greatest portion of the cost of a long-distance telephone call. Even though a long-distance call can be carried very efficiently and cheaply over a digital network, the use of a central gateway to place the call into analog form or convert it from analog to digital form adds significant expense. Thus, until central gateways can be eliminated, the downward trend of long-distance telephone communications (and local calls that must be converted) is limited.
Digital Subscriber Line (DSL) technology is one form of digital telephone service that is quite popular. Even though DSL service can operate over the same physical local loops as POTS, it has a much higher bandwidth, thus allowing many more services to be offered to consumers and businesses. For example, in addition to traditional voice communications, DSL service providers can also offer increased bandwidth for data communications.
In a typical telephone call between a digital telephone service (e.g., DSL) subscriber and a POTS subscriber, a calling party having the digital service initiates a call in digital format over the local loop connecting the calling party to the local telephone company""s central office. At the CO the call is received by a device configured for the digital service. For DSL, the call is received and processed by a DSLAM (DSL Access Multiplexer), which serves as a concentrator for calls involving DSL subscribers. From the DSLAM, the call is transferred to a digital network where a call server or directory server routes the call to the CO serving the called party. At the called party""s CO, a central gateway receives the call, converts it to analog format and feeds it to a CO switch, which places it on the local loop for completion to the called party. Because the call must be processed by the central gateway, which is typically operated by an entity (e.g., the local telephone company) other than the calling party""s digital service provider, the cost is higher than if would be if the digital service provider was able to complete the call without the gateway.
What is needed then is a system and method for enabling telephone communications to be conducted between digital and analog service subscribers without relying on a central gateway. What is also needed is a digital telephone device that is compatible with digital and analog forms of telephone calls. The digital telephone device may be capable of switching calls between the two forms. The device may also be capable of using one or the other form to place a call, depending on system status.
In one embodiment of the invention a system and methods are provided for completing a telephone call between a digital telephone service (e.g., DSL) subscriber and an analog (e.g., POTS) subscriber without the intervention of a central gateway. Illustratively, the routing and completion of the call may be completely, or almost completely, under the control of the digital telephone service provider, thus allowing reduced cost for many local and long-distance telephone communications.
In this embodiment of the invention a DSL service subscriber uses a digital telephone device capable of conducting analog and digital telephone communications simultaneously. The subscriber""s DSL connection to the central office (CO) (or other location at which the DSLAM that services the subscriber is located) includes a digital (i.e., DSL) portion, relatively high in bandwidth, and an analog portion having sufficient bandwidth to carry at least one analog call. In a normal mode of operation all of the subscriber""s outgoing and incoming telephone calls are conducted over the digital portion of the subscriber""s DSL connection. The subscriber normally has no access to the analog portion, which is controlled by the DSL service provider.
When the DSL subscriber places a call to a POTS subscriber, the call is made over the digital portion of the DSL connection to a DSLAM, which transfers the call to a digital network (which may be public, such as the Internet, or private). The call is received by a portal (e.g., a call server or communication server) configured to route telephone calls. The portal determines that the called party is not a subscriber to the digital service (e.g., DSL), or at least not a subscriber to the same digital service as the calling party. However, the portal identifies a digital subscriber served by the same central office as the called party and routes the call to a DSLAM serving that subscriber. This subscriber may be termed a xe2x80x9cpass-throughxe2x80x9d subscriber.
The DSLAM routes the call, still in digital format, to the pass-through subscriber using the digital portion of the DSL connection. At the pass-through subscriber""s digital telephone device, the call is received along with an instruction from the portal to the device to take the analog portion of the pass-through subscriber""s DSL connection off-hook and dial the called party. The call is thus routed from the digital portion back out the analog portion of the pass-through subscriber""s connection to the CO. At the CO the call is received as just another local analog call and is switched to the called party for completion. Any portion(s) of the call may be encrypted or otherwise secured to protect the privacy of the calling and/or called parties.
In one embodiment of the invention a digital telephone device is provided that acts as a limited (e.g., one line) gateway to facilitate the calling method described above. The configuration of the device, and the digital telephone service to which the pass-through party subscribes, prevent the party from accessing calls that pass through its device. The device includes software or firmware that is re-programmable through the DSL connection (e.g., from the portal).
In one embodiment of the invention the device also incorporates one or more subscriber line interface circuits (SLIC), which allow calls to be made over the analog portion of the DSL connection. The device may also incorporate a data port configured to allow a computing device to send and receive data communications.
In one embodiment the device incorporates the ability to fail over from using the digital portion of a DSL connection to the analog portion (e.g., to provide xe2x80x9clife-linexe2x80x9d service). The device may include a port for a handset and/or an analog telephone. If the digital telephone service fails or power for the digital service fails, the analog portion of the subscriber""s DSL connection may be enabled so that the subscriber can at least conduct telephonic communications over the analog portion.
The digital telephone device may also include an LCD, LED or other display, a numeric (and/or alphabetic) keypad, a processor or controller to direct the operation of one or more components, a splitter or filter to divide the analog and digital portions of the DSL connection, a digital (e.g., DSL) modem and a power supply.